A number of types of fluid storage tanks have heretofore been provided, and some of these are intended to be easily transported from one location to another by towing behind a towing vehicle at a time when the tank is empty and between usages thereof. Two such tanks are those which are illustrated and described in U.S. Pat. No. DES.-253,051 and in U.S. Pat. No. 4,318,549. These fluid storage tanks are generally trapezoidally-shaped from the forward end to the rear end, and this enables them to be supported at the rear end upon a pair of ground engaging wheels at a time when the fluid storage tank is to have its front end lifted upwardly, and secured behind a towing vehicle so that the top of the tank becomes substantially horizontal. The tank is intended to be towed while it is empty, and is intended to be rested flatly upon the ground when it is in use for storing the fluid to be dispensed therefrom at a well site or the like.
It has been customary and conventional, and such construction is without exception so far as Applicant is aware, to construct the top of fluid storage tanks of the type described of a flat expanse of metal which constitutes a substantially unitary unbroken expanse from a point relatively near to the rear of the tank to the front of the tank. Thus, the tank top slopes downwardly gradually at a time when the tank is rested upon the ground and fluid is stored therein.
A problem which is confronted not infrequently in the use of trapezoidally-shaped fluid storage tanks of the type described is that of slipping or falling on top of the tank at a time when a person must be at that location for the purpose of gauging the fluid left in the tank, entering the tank for purposes of inspecting certain parts of it, or effecting maintenance to one or more structures located at, or near, the top of the tank. If the tank has been used to store a fluid in inclement weather conditions, under which conditions the top of the tank has become iced or extremely slick, then the danger of the person becoming injured by slipping and falling upon the top of the tank, or even falling or sliding over the side of the tank, are very much increased.